Nitrogen-doped hydrogenated TiO₂ modified with CdS nanorods with enhanced optical absorption, charge separation and photocatalytic hydrogen evolution

In the practical photocatalytic hydrogen evolution process, the light absorption, charge carrier separation and optimizing the activation ability of reactive molecules are the pivotal factors that restrict photocatalytic performance. Hence, we rationally engineer novel CdS/Ti³⁺/N-TiO₂ (TNTC) composite photocatalyst via integrating the evaporation induced self-assembly (EISA) and in-situ hydrothermal method. In the TNTC system, Ti³⁺/O_V and doped N respectively locate at below the conduction band (CB) and above the valence band (VB) of TiO₂ to shorten the band gap from two inverse directions, thereby improving light utilization efficiency. The type II heterojunction TNTC with interfacial coupling effect can foster the spatial charge separation and the Ti³⁺ can form hydrogenation layer to reduce the activation barrier of H₂, which all can improve H₂ evolution capacity. Integrating with the above advantageous qualities, the 10%CdS/Ti³⁺/N-TiO₂ (TNTC10) has the best photocatalytic H₂ evolution activity (1118.5 μmol), which is about 15 and 40 times higher than that of CdS (71.6 μmol) and Ti³⁺/N-TiO₂ (TNT, 27.7 μmol), respectively. Furthermore, we also test the photocatalytic activity of 10%CdS/N-TiO₂ (NTC10) to facilitate comparison with TNTC10. Expectedly, the photocatalytic activity of TNTC10 is 6 times higher than that of NTC10 (178.3 μmol), uncovering that the Ti³⁺ hydrogenated layer plays a pivotal role in boosting the efficiency of H₂ evolution. It is hoped that this work will provide a new cognitive perspective and understanding for building new-fashioned hydrogen evolution photocatalysts.